Flame-resistant polycarbonate ABS molding materials

ABSTRACT

A flame resistant thermoplastic molding composition is disclosed. The composition contains a mixture of two aromatic polycarbonates having differing solution viscosities, a vinyl(co)polymer made from at least two ethylenically unsaturated monomers, a graft polymer obtainable by graft polymerization of at least two monomers selected from chloroprene, 1,3-butadiene, isoprene, styrene, acrylonitrile, ethylene, propylene, vinyl acetate and (meth)acrylates with 1 to 18 carbon atoms in the alcohol component, a phosphorous compound, a fluorinated polyolefin and an inorganic compound with an average particle size no greater than 200 nm. The inventive composition is additionally characterized in its improved stress cracking resistance.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

The present patent application claims the right of priority under 35U.S.C. 119 and 35 U.S.C. 365 of International Application No.PCT/EP98/04731, filed Jul. 29, 1998, which was published in German asInternational Patent Application No. WO 99/07791 on Feb. 18, 1999, whichis entitled to the right of priority of German Patent Application No.197 34 666.9, filed Aug. 11, 1997.

The present invention relates to polycarbonate/ABS moulding compositionswhich have been rendered flame-resistant with phosphorus compounds,which have an outstanding set of mechanical properties, in particular anoutstanding resistance to stress cracking, and are flame-resistant.

EP-A 0 174 493 describes flame-resistant, halogen-containing polymermixtures consisting of aromatic polycarbonate, styrene-containing graftcopolymer, monophosphates and a specific polytetrafluoroethyleneformulation. Although these mixtures have adequate fire resistance andmechanical properties, the surface quality of moulded items may beimpaired when using high processing temperatures. The moulded items alsoexhibit some deficiencies in stress crack resistance.

EP-A 0 363 608 describes polymer mixtures consisting of aromaticpolycarbonate, styrene-containing copolymer or graft copolymer andoligomeric phosphates as flame-resistant additives. The stress crackresistance of these mixtures is often not sufficient to enable theproduction of thin-walled housing parts.

EP-A 771 851 describes moulding compositions which contain aromaticpolycarbonate, graft copolymer based on a diene rubber, an SANcopolymer, a phosphate and tetrafluoroethylene polymers, wherein thepolycarbonate has a variety of molecular weights. However, no veryfinely divided inorganic compounds are described as a constituent of themoulding compositions.

The object of the present invention was to provide flame-resistantpolycarbonate/ABS moulding compositions which have outstanding stresscrack resistance as well as very good processing properties and whichare particularly suitable for producing thin-walled housing parts.

Surprisingly it was found that polycarbonate/ABS moulding compositionswhich have a greatly improved stress crack resistance are produced byusing specific mixtures of polycarbonates, each with clearlydifferentiated solution viscosities, combined with very finely dividedinorganic compounds.

Therefore the invention provides flame-resistant, thermoplastic mouldingcompositions containing

A 5 to 95, preferably 10 to 90, in particular 20 to 80 parts by weightof a mixture of two aromatic polycarbonates A.1 and A.2 with differentsolution viscosities, wherein

1. the relative solution viscosity of A.1 is 1.18 to 1.24,

2. the relative solution viscosity of A.2 is 1.24 to 1.34 and

3. the difference between the relative solution viscosities of A.1 andA.2 is equal to or greater than 0.06,

wherein one or more further polycarbonates may be added to the mixtureof A.1 and A.2,

B 0 to 50, preferably 1 to 30, in particular 2 to 25 parts by weight ofa (co)polymer consisting of 1 or at least 2 ethylenically unsaturatedmonomers.

C 0.5 to 60, preferably 1 to 40, in particular 2 to 30 parts by weightof graft polymers, obtainable by graft polymerisation of at least twomonomers selected from the group consisting of chloroprene, butadiene,isoprene, styrene, acrylonitrile, ethylene, propylene, vinyl acetate and(meth)acrylates with 1 to 18 carbon atoms in the alcohol component,

D 0.5 to 20 parts by weight, preferably 1 to 18 parts by weight, inparticular 2 to 15 parts by weight of a phosphorus compound of theformula (1)

 in which

R¹, R²′ R³ and R⁴, independently of each other, represent an optionallyhalogenated C₁-C₈ alkyl group, or a C₅-C₆ cycloalkyl, C₆-C₂₀ aryl, orC₇-C₁₂ aralkyl group, each optionally substituted by halogen and/orC₁-C₄ alkyl groups

n each, independently, represents 0 or 1

N is 0 to 30 and

X represents a mono- or polynuclear aromatic group with 6 to 30 carbonatoms,

E 0.05 to 5 parts by weight, preferably 0.1 to 1 part by weight, inparticular 0.1 to 0.5 parts by weight of a fluorinated polyolefin,

F 0.01 to 50 parts by weight, preferably 0.1 to 10 parts by weight per100 parts by weight of A to E of very finely divided inorganic compoundwith an average particle diameter of less than or equal to 200 nm,preferably less than or equal to 150 nm, in particular less than orequal to 100 nm.

The sum of all the parts by weight of A+B+C+D+E+F is 100.

Moulding compositions according to the invention, due to theirexceptional flame resistance, stress crack resistance and very goodprocessing properties are particularly suitable for preparingthin-walled moulded articles (housing parts for data processing units),where high processing temperatures and pressures lead to considerablestrain on the material used.

Component A

Thermoplastic, aromatic polycarbonates which are suitable for use ascomponent A according to the invention are those based on diphenols ofthe formula (II)

in which

A represents a single bond or a C₁-C₅ alkylene, C₂-C₅ alkylidene, C₅-C₆cycloalkylidene, —S—, —SO₂—, —O—, —CO—or C₆-C₁₂ arylene group,

B represents chlorine or bromine,

X is 0, 1 or 2 and

P is 1 or 0

or alkyl substituted dihydroxyphenylcycloalkanes of the formula (III)

 in which

R¹¹ and R¹², independently of each other, each represent hydrogen, ahalogen, preferably chlorine or bromine, or a C₁-C₈ alkyl, preferablyC₁-C₄ alky, C₅-C₆ cycloalkyl, C₆-C₁₀ aryl, preferably phenyl, or C₇-C₁₂aralkyl, preferably a phenyl-C₁-C₄ alkyl, in particular benzyl, group

m is an integer, from 4 to 7, preferably 4 or 5,

R¹³ and R¹⁴ can be individually chosen for each Z, and, independently ofeach other, represent hydrogen or a C₁-C₆ alkyl group, preferablyhydrogen, methyl or ethyl,

and

z represents carbon, with the proviso that, on at least one atom Z, R¹³and R¹⁴ simultaneously represent an alkyl group.

Suitable diphenols of the formula (II) are e.g. hydroquinone,resorcinol, 4,4′dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)-propane,2,4-bis-(4-hydroxyphenyl)-2-methylbutane,1,1-bis-(4-hydroxyphenyl)-cyclohexane,2,2-bis-(3-chloro-4-hydroxyphenyl)-propane,2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

Preferred diphenols of the formula (II) are2,2-bis4-hydroxyphenyl)propane,2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and1,1-bis-(4hydroxyphenyl)-cyclohexane.

Preferred diphenols of the formula (III) aredihydroxydiphenylcycloalkanes with 5 or 6 ring carbon atoms in thecycloaliphatic grouping (m=4 or 5 in formula (III)) such as for examplediphenols with the formulae

wherein 1,1-bis-(4-hydroxyphenyl)-3 ,3,5-trimethylcyclohexane (formula(IIIa)) is particularly preferred.

Polycarbonates which are suitable for use as component A according tothe invention may be branched in a known way, that is preferably by theincorporation of 0.05 to 2.0 mol %, with respect to the sum of diphenolsused, of tri-functional or more than tri-functional compounds, e.g.those with three or more than three phenolic groups, such as for example

phloroglucine

4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene

4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane

1,3,4-tri-(4-hydroxyphenyl)-benzene

1,1,1-tri-(4-hydroxyphenyl)-ethane

tri-(4-hydroxyphenyl)-phenylmethane

2,2-bis-(4,4-bis-(4-hydroxyphenyl)-cyclohexyl)-propane

2,4-bis-(4,4-bis-(4-hydroxyphenyl)-isopropyl)-phenol

2,6-bis-(2-hydroxy-5′-methylbenzyl)-4-methyl-phenol

2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane

hexa-(4-(4-hydroxyphenylisopropyl)-phenyl) orthoterephthalate

tetra-(4-hydroxyphenyl)-methane

tetra-(4-(4-hydroxyphenylisopropyl)phenoxy)-methane and

1,4-bis-((4′-,4′-dihydroxytriphenyl)-methyl)-benzene

A few other trifunctional compounds are 2,4-dihydroxybenzoic acid,trimesic acid, cyanuric chloride and 3,3-bis-(3methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

Preferred polycarbonates, in addition to bisphenol-A homopolycarbonate,are copolycarbonates of bisphenol-A with up to 15 mol %, with respect tothe molar sum of diphenols, of2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

Some of the aromatic polycarbonates in component A may be exchanged foraromatic polyestercarbonates.

Aromatic polycarbonates in component A may also contain polysiloxaneblocks. The preparation of these is described, for example, in DE-OS 3334 872 and U.S. Pat. No. 3,821,325.

Aromatic polycarbonates and/or aromatic polyestercarbonates inaccordance with component A are known from the literature or can beprepared by processes known from the literature (to prepare aromaticpolycarbonates, see for example, Schnell “Chemistry and Physics ofPolycarbonates” Interscience Publishers 1964 and DE-AS 1 495 626, DE-OS2 232 877, DE-OS 2 703 376, DE-OS 2 714 544, DE-OS 3 000 610, DE-OS 3832 396; to prepare aromatic polyestercarbonates, see e.g. DE-OS 3 077934).

Aromatic polycarbonates and/or polyestercarbonates are prepared, forexample, by reacting diphenols with carbonic acid halides, preferablyphosgene, and/or with aromatic dicarboxylic acid dihalides, preferablybenzene dicarboxylic acid halides, by the phase interface process,optionally using chain terminators and optionally using trifunctional ormore than trifunctional branching agents.

Polycarbonates A.1 and A.2 preferably have the same structures, i.e.they are built up from the same monomers.

Particularly preferably, both polycarbonates A.1 and A.2 and also theoptionally further added polycarbonate A are built up from the samemonomers, i.e. they have the same chemical structure.

A further polycarbonate is preferably added up to an amount of 30 wt. %(with respect to the amount of A.1 and A.2).

With respect to the mixture of polycarbonates A.1 and A.2, theproportion by weight of A.1 is 5 to 95, preferably 10 to 75 wt %, inparticular 10 to 35 wt. %, and the proportion by weight of A.2 is 95 to5, preferably 90 to 25 wt %, in particular 90 to 65 wt. %.

The mixture of polycarbonates A.1 and A.2 is characterised in that therelative solution viscosity of A.1 is, 1.18 to 1.24, that the relativesolution viscosity of A.2 is 1.24 to 1.34 and that the differencebetween the relative solution viscosities of A.1 and A.2 is greater thanor equal to 0.06, in particular greater than or equal to 0.09, i.e. therelative solution viscosity of (A.2) minus the relative solutionviscosity of (A.1) is ≧0.06, in particular ≧0.09. The relative solutionviscosity is measured in CH₂Cl₂ as solvent at 25° C., at a concentrationof 0.5 g/l 00 ml.

One or both polycarbonate constituents A.1 or A.2 in the mixture may bea recycled polycarbonate. Recycled polycarbonates are understood to bethose products which have already passed through one processing and lifecycle and from which adhering impurities have been sufficiently wellremoved, by means of a special working-up process, for them to besuitable for further use.

Component B

Thermoplastic polymer B comprises (co)polymers of one or at least twoethylenically unsaturated monomers (vinyl monomers) such as for examplestyrene, α-methylstyrene, ring-substituted styrenes (e.g. halogen and/oralkyl ring-substituted), acrylonitrile, methacrylonitrile, methylmethacrylate, maleic anhydride, N-subsfituted maleic imide and(meth)acrylates with 1 to 18 carbon atoms in the alcohol component.

(Co)polymers in accordance with component B are resinous, thermoplasticand rubber-free. The moulding compositions may also contain different(co)polymers B.

Preferred vinyl (co)polymers B are those consisting of at least onemonomer from the set consisting of styrene, a-methylstyrene,ring-substituted styrene and/or methyl methacrylate (B.1) with at leastone monomer from the set consisting of acrylonitrile, methacrylonitrile,methyl methacrylate, maleic anhydride and/or N-aryl substituted maleicimide (B.2).

The concentration of monomers B.1 in the (co)polymer is preferably 50 to99, in particular 60 to 95 wt. %, that of monomers B.2 is preferably 1to 50, in particular 5 to 40 wt. %.

Particularly preferred (co)polymers B are those consisting of styrenewith acrylonitrile and optionally methyl methacrylate, ofα-methylstyrene with acrylonitrile and optionally with methylmethacrylate, or of styrene and α-methylstyrene with acrylonitrile andoptionally methyl methacrylate.

(Co)polymers in accordance with component B are known and can beprepared by radical polymerisation, in particular by emulsion,suspension, solution or bulk polymerisation. (Co)polymers in accordancewith component B preferably have molecular weights {overscore (M)}_(w)(weight average, determined by light scattering or sedimentation)between 15,000 and 200,000.

Particularly preferred (co)polymers B according to the invention arealso random copolymers built up from styrene and maleic anhydride whichare preferably prepared by continuous bulk or solution polymerisationwith incomplete conversion of the corresponding monomers.

The proportions of the two components in suitable random copolymersaccording to the invention and built up from styrene and maleicanhydride may vary within wide limits. The preferred concentration ofmaleic anhydride is 5 to 25 wt. %. Instead of styrene, the polymers mayalso contain ring-substituted styrenes such as p-methylstyrene,2,4-dimethylstyrene and other substituted styrenes such asα-methylstyrene.

The molecular weight (number average {overscore (M)}_(n)) of randomcopolymers according to the invention built up from styrene and maleicanhydride in accordance with component B may vary over a wide range. Therange is preferably from 60,000 to 200,000. The intrinsic viscosity ofthese products is preferably 0.3 to 0.9 (measured in dimethylformamideat 25° C.; see Hoffman, Krömer, Kuhn, Polymeranalytik I, Stuttgart 1977,pages 316 et seq).

Component C

Component C in accordance with the invention is a graft polymer. Theseinclude graft copolymers with rubber-elastic properties which aresubstantially obtainable from at least two of the following monomers:chloroprene, 1,3-butadiene, isoprene, styrene, acrylonitrile, ethylene,propylene, vinyl acetate and (meth)acrylates with 1 to 18 carbon atomsin the alcohol component; that is polymers such as are described e.g. in“Methoden der Organischen Chemie” (Houben-Weyl), Volume 14/1, GeorgThieme-Verlag, Stuttgart 1961, pages 393-406 and in C.B.Bucknall“Toughened Plastics”, Appl. Science Publishers, London 1977. Preferredpolymers C are partially cross-linked and have gel contents of more than20 wt. %, preferably more than 40 wt. %, in particular more than 60 wt.%.

Preferred graft polymers C comprise:

C.1 5 to 95, preferably 30 to 80, parts by weight of a mixture of

C.1.1 50 to 99 parts by weight of styrene, α-methylstyrene, halogen ormethyl ring-substituted styrenes, methyl methacrylate or mixtures ofthese compounds and

C.1.2 1 to 50 parts by weight of acrylonitrile, methacrylonitrile,methyl methacrylate, maleic anhydride, C₁-C₄ alkyl- orphenyl-N-substituted maleic imides or mixtures of these compounds on

C.2 5 to 95, preferably 20 to 70, parts by weight, of a polymer based ondiene and/or an alkyl acrylate with a glass transition temperature below−10° C.

Preferred graft polymers C are e.g. substrates C.2 such aspolybutadienes, butadiene/styrene copolymers and acrylate rubbersgrafted with styrene and/or acrylonitrile and/or alkyl (meth)acrylates,i.e. copolymers of the type described in DE-OS 1 694 173 (=U.S. Pat No.3,564,077); or polybutadienes, butadiene/styrene orbutadiene/acrylonitrile copolymers, polyisobutenes or polyisoprenesgrafted with alkyl acrylates or alkyl methacrylates, vinyl acetate,acrylonitrile, styrene and/or alkylstyrenes, such as are described e.g.in DE-OS 2 348 377 (=U.S. Pat. No. 3,919,353).

Particularly preferred polymers C are e.g. ABS polymers such as aredescribed e.g. in DE-OS 2 035 390 (=U.S. Pat. No. 3,644,574) or in DE-OS2 248 242 (=GB-PS 1 409 275).

Particularly preferred graft polymers C are obtainable by a graftingreaction of

α 10 to 70, preferably 15 to 50, in particular 20 to 40 wt. %, withrespect to graft polymer C, of at least one (meth)acrylate or 10 to 70,preferably 15 to 50, in particular 20 to 40 wt. %, of a mixture of 10 to50, preferably 20 to 35 wt. %, with respect to the mixture, ofacrylonitrile or (meth)acrylate and 50 to 90, preferably 65 t6 80 wt. %,with respect to the mixture, of styrene, as applied graft C.1, on

β 30 to 90, preferably 50 to 85, in particular 60 to 80 wt. %, withrespect to graft polymer C, of a butadiene polymer with at least 50 wt.%, with respect to β, of butadiene groups, as graft substrate C.2,

wherein the gel fraction in the graft substrate 0 is preferably at least70 wt. % (measured in toluene), the degree of grafting G is 0.15 to 0.55and the average particle diameter d₅₀ of the graft polymer C.2 is 0.05to 2 μm, preferably 0.1 to 0.6 μm.

(Meth)acrylates a are esters of acrylic acid or methacrylic acid withmonohydric alcohols with 1 to 18 carbon atoms. Methyl-, ethyl- andpropyl methacrylate, n-butyl acrylate, t-butyl acrylate and t-butylmethacrylate are particularly preferred.

Graft substrate β may contain, in addition to butadiene groups, up to 50wt. %, with respect to β, of groups from other ethylenically unsaturatedmonomers such as styrene, acrylonitrile, esters of acrylic ormethacrylic acid with 1 to 4 carbon atoms in the alcohol components(such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethylmethacrylate), vinyl esters and/or vinyl ethers. The preferred graftsubstrate β consists of pure polybutadiene.

The degree of grafting G is the ratio by weight. of grafted monomers tograft substrate and is dimensionless.

The average particle size d₅₀ is the diameter above and below which 50%of the particle diameters are located. It may be determined by means ofultracentrifuge measurements (W. Scholtan, H. Lange, Kolloid, Z. und Z.Polymere 250 (1972) 782-796).

Particularly preferred polymers C are also e.g. graft polymers of

τ20 to 90 wt. %, with respect to component C, of acrylate rubber with aglass transition temperature below −20° C. as graft substrate C.2 and

δ6 10 to 80 wt. %, with respect to component C, of at least onepolymerisable ethykenically unsaturated monomer as graft monomer C. 1.

Acrylate rubbers T in polymers C are preferably polymers of alkylacrylates, optionally with up to 40 wt. % with respect to τ, of otherpolymerisable ethylenically unsaturated monomers. Preferredpolymerisable acrylates include C₁-C₈ alkyl esters, for example methyl,ethyl, butyl, n-octyl and 2-ethylhexyl esters; halogenated alkyl esters,preferably halogenated C₁-C₈ alkyl esters such as chloroethyl acrylate,and mixtures of these monomers.

In order to cross-link the product, monomers with more than onepolymerisable double bond may be copolymerised. Preferred examples ofcross-linking monomers are esters of unsaturated monocarboxylic acidswith 3 to 8 carbon atoms and unsaturated monohydric alcohols with 3 to12 carbon atoms or saturated polyols with 2 to 4 OH groups and 2 to 20carbon atoms such as, for example, ethyleneglycol dimethacrylate, allylmethacrylate; polyunsaturated heterocyclic compounds such as, forexample, trivinyl and triallyl cyanurate; polyfunctional vinyl compoundssuch as divinyl- and trivinylbenzene; but also triallyl phosphate anddiallyl phthalate.

Preferred cross-linking monomers are allyl methacrylate, ethyleneglycoldimethylacrylate, diallyl phthalate and heterocyclic compounds whichcontain at least 3 ethylenically unsaturated groups.

Particularly preferred cross-linking monomers are the cyclic monomerstriallyl cyanurate, triallyl isocyanurate, trivinyl cyanurate,triacryloyl hexahydro-s-triazine, triallylbenzenes.

The amount of cross linking monomers is preferably 0.02 to 5, inparticular 0.05 to 2 wt. %, with respect to graft substrate τ.

In the case of cyclic cross-linking monomers with at least 3ethylenically unsaturated groups, it as advantageous to restrict theamount to less than 1 wt. % of the graft substrate τ.

Preferred “other” polymerisable ethylenically unsaturated monomers,apart from acrylates, which may optionally be used to prepare graftsubstrates τ are e.g. acrylonitrile, styrene, α-methylstyrene,acrylamide, vinyl C₁-C₆ alkyl ethers, methyl methacrylate, butadiene.Preferred acrylate rubbers for use as graft substrates r are emulsionpolymers which have a gel content of at least 60 wt. %.

Further suitable graft substrates in accordance with C.2 are siliconerubbers with graft-active sites such as are described in DE-OS 3 704657, DE-OS 3 704 655, DE-OS 3 631 540 and DE-OS 3 631 539.

The gel content of graft substrate C.2 is determined at 25° C. indimethylformamide (M. Hoffman, H. Krömer, R. Kuhn, Polymeranalytik I andII, Georg Thieme-Verlag, Stuttgart 1977).

The graft polymer C may be prepared by known processes such as bulk,suspension, emulsion or bulk-suspension processes.

Since, as is known, the grafting monomers cannot be grafted onto thegrafting substrate completely and absolutely during the graftingreaction, graft polymers C according to the invention are alsounderstood to be those products which are obtained by the polymerisationof graft monomers in the presence of the graft substrate.

Component D

Moulding compositions according to the invention contain, asflame-resistant agents, at least one organic phosphorus compound or amixture of organic phosphorus compounds of the formula (1).

In the formula, R¹, R², R³ and R⁴ are defined in the same way as givenabove. R¹, R², R³ and R⁴ preferably represent a C₁-C₄ alkyl group or aphenyl, naphthyl or phenyl-C₁-C₄ alkyl group. The aromatic groups R¹,R², R³ and R⁴ for their part may be substituted by halogen and/or alkylgroups (preferably C₁-C₄ alkyl groups). Particularly preferred arylgroups are cresyl, phenyl, xylenyl, propylphenyl or butylphenyl and thecorresponding brominated and chlorinated derivatives thereof.

X in formula (I) represents a mono- or polynuclear aromatic group with 6to 30 carbon atoms. This is preferably derived from diphenyls inaccordance with formula (II) such as e.g. bisphenol-A, resorcinol orhydroquinone or their chlorinated or brominated derivatives.

N in formula (I) may, each independently, be 0 or 1; n is preferably 1.

N may have any value from 0 to 30.

In the case of mixtures of phosphorus compounds, N may have an averagevalue of 0 to 30, preferably an average value of 0.3 to 20, inparticular 0.5 to 10, especially 0.5 to 6. Monophosphorus compoundsand/or oligomeric phosphorus compounds may be contained in this mixture.In the event that N=0, formula (1) describes monophosphorus compounds.

Phosphorus compounds of the formula (I) are preferablytributylphosphate, tris-(2-chloroethyl) phosphate,tris-(2,3-dibromopropyl) phosphate, triphenyl phosphate, tricresylphosphate, diphenylcresyl phosphate, diphenyloctyl phosphate,diphenyl-2-ethylcresyl phosphate, tri-(isopropylphenyl) phosphate,halogen substituted aryl phosphates, dimethyl methylphosphonate,diphenyl methylphosphonate, diethyl phenylphosphonate,triphenylphosphine oxide and/or m-phenylene-bis(diphenyl) phosphate.

Mixtures of phosphorus compounds of the formula (I) with N values from0.5 to 10, in particular 0.5 to 6, are preferred.

Monomeric and oligomeric phosphorus compounds of the formula (1) arepreferably chosen in the mixture, so that a synergistic effect isproduced. The mixture generally consists of 10 to 90 wt. % of dimersand/or oligomers and 90 to 10 wt. % of monophosphorus compounds,preferably monophosphate compounds of the formula (I). Themonophosphorus compounds are preferably mixed within the range from 12to 50, preferably 14 to 40, in particular 15 to 40 wt. %, with thecomplementary amount of oligomeric phosphorus compounds.

Phosphorus compounds in accordance with component D are known (see e.g.EP-A 363 608, EP-A 640 655) or can be prepared by known methods in ananalogous manner (e.g. Ulhmanns Encyklopadie der technischen Chemie,Vol. 18, page 301 et seq 1979; Houben-Weyl, Methoden der organischenChemie, Vol. 12/1, p. 43; Beilstein Vol. 6, p. 177).

Component E

Fluorinated polyolefins E are high molecular weight compounds and haveglass transition temperatures above -30° C., generally above 100° C.,fluorine contents of preferably 65 to 76, in particular 70 to 76 wt. %,average particle diameters d₅₀ of 0.05 to 1000, preferably to 0.08 to 20μm. In general, the fluorinate polyolefins E have a density of 1.2 to2.3 g/cm³.

Preferred fluorinated polyolefins E are polytetrafluoroethylene,polyvinylidene fluoride, tetrafluoroethylene/hexafluoropropylenecopolymers and ethylene/tetrafluoroethylene copolymers.

Fluorinated polyolefins are known (see “Vinyl and Related Polymers” bySchildknecht, John Wiley & Sons, Inc., New York, 1962, pp 484-494;“Fluoropolymers” by Wall, Wiley-Interscience, John Wiley & Sons Inc.,New York, Vol. 13, 1970, pp 623-654; “Modem Plastics Encyclopedia” 1970to 1971, Vol. 47, No. 10A, October 1970, McGraw-Hill, Inc., New York, pp134 and 774; “Modern Plastics Encyclopedia” 1975 to 1976, October 1975,Vol. 52, No. 10A, McGraw-Hill, Inc., New York, pp 27,28 and 472 and U.S.Pat. No. 3 671 487, 3 723 373 and 3 838 092).

They can be prepared by known processes, for example by polymerisationof tetrafluoroethylene in aqueous medium with a free radical-formingcatalyst, for example sodium, potassium or ammonium peroxydisulfate atpressures of 7 to 71 kg/cm² and at temperatures of 0 to 200° C.,preferably at temperatures of 20 to 100° C. (See e.g. U.S. Pat. No. 2393 967 for more details). Depending on the form actually used, thedensity of these materials may be between 1.2 and 2.3 g/cm , and theaverage particle size between 0.05 and 1000 μm.

Preferred fluorinated polyolefins E according to the invention aretetrafluoroethylene polymers and have average particle diameters of 0.05to 20 μm, preferably 0.08 to 10 μm, and a density of 1.2 to 1.9 g/cm³and are preferably used in the form of a coagulated mixture of emulsionsof tetrafluoroethylene polymers E with emulsions of graft polymers C.

Suitable tetrafluoroethylene polymer emulsions are commerciallyavailable products and are sold for example by Du Pont as Teflon® 30N.

Suitable fluorinated polyolefins E which can be used in a powder formare tetrafluoroethylene polymers with average particle diameters of 100to 1000 μm and densities of 2.0 g/cm³ to 2.3 g/cm³.

To prepare a coagulated mixture of C and E, an aqueous emulsion (latex)of a graft polymer C with an average latex particle diameter of 0.05 to2 μm, in particular 0.1 to 0.6 μm, is first mixed with a finely dividedemulsion of a tetrafluoroethylene polymer E in water with averageparticle diameters of 0.05 to 20 μm, in particular 0.08 to 10 μm.Suitable tetrafluoroethylene polymer emulsions generally have solidscontents of 30 to 70 wt. %, in particular 50 to 60 wt. %.

The aqueous emulsion of graft polymer C has a solids content of 25 to 60wt. %, preferably 30 to 45 wt. %, in particular 30 to 35 wt. %.

The data given on amounts in the description of component C does notinclude the proportion of graft polymer in the coagulated mixture ofgraft polymer and fluorinated polyolefins.

In the emulsion mixture, the ratio by weight of graft polymer C totetrafluoroethylene polymer E is 95:5 to 60:40. The emulsion mixture iscoagulated in a known manner, for example by spray drying, freeze dryingor coagulating by adding inorganic or organic salts, acids, bases ororganic water-miscible solvents such as alcohols or ketones, preferablyat temperatures of 20 to 150° C. in particular 50 to 100° C. If requireddrying may be performed at 50 to 200° C., preferably 70 to 100° C.

Component F

Very finely divided inorganic compounds in accordance with component Fconsist of compounds of one or more metals from groups IA to SA and IBto 8 in Mendelejew's periodic system of elements, preferably groups 2Ato 5A and 4B to 8, in particular 3A to 5A and 4B to 8, with at least oneelement selected from the group consisting of oxygen, sulfur, boron,phosphorus, carbon, nitrogen, hydrogen or silicon.

Preferred compounds are for example oxides, hydroxides, hydrated oxides,sulfates, sulfites, sulfides, carbonates, carbides, nitrates, nitrites,nitrides, borates, silicates, phosphates, hydrides, phosphites orphosphonates.

Preferred very finely divided inorganic compounds are for example TiN,TiO₂, SnO₂, WC, ZnO, Al₂O₃, AlO(OH), ZrO₂, Sb₂O₃, SiO₂, iron oxides,Na₂SO₄, BaSO₄, vanadium oxides, zinc borate, silicates such as aluminumsilicates, magnesium silicates, and one-, two- or three-dimensionalsilicates. Mixtures and doped compounds may also be used. Furthermorethese nano-scale particles may be surface-modified with organicmolecules in order to produce better compatibility with the matrix.Hydrophobic or hydrophilic organic surfaces can be produced in this way.

The average particle diameters are less than or equal to 200 nm,preferably less than or equal to 150 nm, in particular from 1 to 100 nm.

The particle size and particle diameter refer to the average particlediameter d₅₀, determined by ultracentrifuge measurements in accordancewith W. Scholtan et al Kolloid-Z und Z. Polymere 250 (1972), pp 782-796.

The inorganic compounds may be used as powders, pastes, sols,dispersions or suspensions. Powders can be obtained by precipitationfrom dispersions, sols or suspensions.

The powders can be incorporated into the thermoplastic plastics usingconventional processes, for example by direct compounding or extrudingof the constituents in the moulding composition and the very finelydivided organic powders. A preferred process is the production of amaster batch, e.g. the coprecipitation of dispersions of components B orC with dispersions, suspensions, pastes or sols of the very finelydivided inorganic materials in flame-resistant additives, otheradditives, monomers, solvents or in thermoplastics A.

Moulding compositions according to the invention may contain at leastone of the conventional additives such as lubricants and mould releaseagents, nucleating agents, anti-static agents, stabilisers and dyes andpigments.

Moulding compositions according to the invention may also containflame-resistant compounds which are different from those of the formula(I) in an amount of up to 20 parts by weight. Synergisticflame-resistant agents are preferred. The following are mentioned by wayof example as further flame-resistant agents; organic halogenatedcompounds such as decabromobisphenylether, tetrabromobisphenol,inorganic halogen compounds such as ammonium bromide, nitrogen compoundssuch as melamine, melamine-formaldehyde resins or siloxane compounds.Moulding compositions according to the invention may optionally containinorganic substances which differ from the inorganic compounds F, suchas for example inorganic hydroxide compounds such as magnesium andaluminium hydroxide, inorganic compounds such as aluminium oxide,antimony oxides, barium metaborate, hydroxyantimonate, zirconium oxide,zirconium hydroxide, molybdenum oxide, ammonium molybdate, zinc borate,ammonium borate and tin oxide.

Moulding compositions according to the invention containing components Ato F and optionally further known additives such as stabilisers, dyes,pigments, lubricants and mould release agents, nucleating agents andanti-static agents, are prepared by mixing the particular constituentsin a known manner and melt-compounding and melt-extruding attemperatures of 200 to 300° C. in conventional equipment such asinternal compounders, extruders and twin-shaft screws, wherein componentE is preferably used in the form of the coagulated mixture mentionedabove.

Mixing the individual constituents may take place in a known manner,either in sequence or simultaneously, in fact either at about 20° C.(room temperature) or also at higher temperatures.

Moulding compositions in the present invention may be used to preparemoulded items of any type. Moulded items can be produced in particularby injection moulding. Examples of moulded items which can be producedare: housing parts of any kind, e.g. for domestic equipment such asjuice extractors, coffee machines, mixers, for office machines such ascomputers, printers, monitors or copiers or cladding sheets for thebuilding sector and parts for the automobile sector. They may also beused in the electrical engineering sector because they have very goodelectrical properties.

The moulding compositions are particularly suitable for producingthin-walled moulded items (e.g. parts for housings for data processingunits), where particularly high specifications relating to flowbehaviour and stress crack resistance are required of the plastics used.

Another form of processing is the production of moulded items bythermoforming from previously prepared sheets or films.

The present invention also provides, therefore, use of the mouldingcompositions according to the invention for preparing moulded items ofany type, preferably those mentioned above, and moulded items made fromthe moulding compositions according to the invention.

EXAMPLES Component A

A

Linear polycarbonate based on bisphenol-A with a relative solutionviscosity of 1.252, measured in CH₂Cl₂ as solvent at 25° C. and at aconcentration of 0.5 g/100 ml.

A.1

Linear polycarbonate based on bisphenol-A with a relative solutionviscosity of 1.284, measured in CH₂Cl₂ as solvent at 25° C. and at aconcentration of 0.5 g/100 ml.

A.2

Linear polycarbonate based on bisphenol-A with a relative solutionviscosity of 1.200, measured in CH₂Cl₂ as solvent at 25° C. and at aconcentration of 0.5 g/100 ml.

Component B

Styrene/acrylonitrile copolymer with a styrene/acrylonitrile ratio of72:28 and an intrinsic viscosity of 0.55 dl/g (measured indimethylformamide at 20° C.).

Component C

Graft polymer of 45 parts by weight of a copolymer of styrene andacrylonitrile in the ratio 72:28 on 55 parts by weight of particulatecross-linked polybutadiene rubber (average particle diameter d₅₀=0.4μm), prepared by emulsion polymerisation.

Component D

Component E

Tetrafluoroethylene polymer as a coagulated mixture formed from an SANgraft polymer emulsion in accordance with component C in water and atetrafluoroethylene polymer emulsion in water. The ratio by weight ofgraft polymer C to tetrafluoroethylene polymer E in the mixture is 90wt. % to 10 wt. %. The tetrafluoroethylene polymer emulsion has a solidscontents of 60 wt. %, the average particle diameter is between 0.05 and0.5 μm. The SAN graft polymer emulsion has a solids content of 34 wt. %and an average latex particle diameter of 0.4 μm.

Preparation of E

The emulsion of the tetrafluoroethylene polymer (Teflon 30N from DuPont) is mixed with the emulsion of the SAN graft polymer C andstabilised with 1.8 wt. %, with respect to the polymer solids, ofphenolic anti-oxidants. The mixture is coagulated at 85 to 95° C. usingan aqueous solution of MgSO₄ (Epsom salts) and acetic acid at pH 4 to 5,filtered and washed until virtually free of electrolytes. Then the majorproportion of water is removed by centrifuging and the product is driedto a powder at 100° C.

This powder can then be compounded with the other components in theequipment described.

Component F

Pural 200, an aluminium oxide hydroxide (Condea Co. Hamburg, Germany) isused as the very finely divided inorganic compound. The average particlesize of the product is about 50 nm.

PREPARATION AND TESTING OF THE MOULDING COMPOSITIONS ACCORDING TO THEINVENTION

Components A to F are mixed on a 3 litre internal compounder. Themoulded items are prepared in an injection moulding machine, type Arburg270E, at 260° C.

The notched impact resistance is determined in accordance with ISO 1801A method using rods with the dimensions 80×10×4 mm³ at roomtemperature.

The Vicat B softening point is determined in accordance with DIN 53 460.

The stress crack characteristics are tested using rods with thedimensions 80×10×4 mm³ with a bulk temperature of 260° C. A mixture of60 vol. % toluene and 40 vol. % isopropanol is used as the test medium.The specimens are pre-stretched using a template shaped in a circulararc and stored together for 5 minutes at room temperature in the testmedium. The extent of pre-stretching ε_(x) is 0.2 to 2.4%. The stresscrack characteristics are assessed by the production of cracks orfractures as a function of the degree of pre-stretching.

The composition of the materials tested and the data obtained aresummarised in the following table 1.

It can be seen from the table that the moulding compositions accordingto the invention have a very good combination of mechanical properties,in particular an unexpected improvement in stress crack resistance and agood flame resistance as compared with moulding compositions which donot contain any very finely divided inorganic powder (component F).

TABLE 1 Composition and properties of polycarbonate/ABS mouldingcompositions Example 3 1 2 According to the Comparison Comparisoninvention Components (parts by weight) A 79 — — A1 — 49 49 A2 — 30 30 B5 5 5 C 5 5 5 D 5.5 5.5 5.5 E 3 3 3 F — — 1.0 Mould release agent 0.50.5 0.5 η_(rel) 1.252 1.252 1.252 Properties: Vicat/B₁₂₀ (° C.) 114 115115 Notched impact resistance: (kJ/m²) 44 46 46 ESC screening BR 5:00 5min/1.0% ESC screening BR 5:00 KR + OR 5 min/0.8% ESC screening BR 3:14KR + OR 5 min/0.6 % ESC screening KR 5 min/0.4% MVI 240° C./5 kg 16.016.4 16.6 ml/10 min Fire V-2 nb* V-0 UL 94 V (1.6 mm) *nb = notresistant

Abbreviations in Table 1 relating to stress crack characteristics aredefined as follows.

ESC screening=Environmental Stress Cracking screening.

BR=Break 1

BR 5:00=The test specimen broke at five (5) minutes in the test medium.

BR 3:14=The test specimen broke at three (3) minutes, fourteen (14)seconds in the test medium. C

KR=Edge Cracks.

OR=Surface Cracks.

What is claimed is:
 1. A flame-resistant, thermoplastic moldingcomposition containing: A 5 to 95 parts by weight of a mixture of twoaromatic polycarbonates A.1 and A.2 with different solution viscosities,wherein
 1. the relative solution viscosity of A.1 is 1.18 to 1.24, 2.the relative solution viscosity of A.2 is 1.24 to 1.34, and
 3. thedifference between the relative solution viscosities of A.1 and A.2 isequal to or greater than 0.06, wherein one or more furtherpolycarbonates may be added to the mixture of A.1 and A.2, the relativesolution viscosities of A.1 and A.2 being measured in CH₂Cl₂ at 25° C.and at a concentration of 0.5 g/100 ml; B 0 to 50 parts by weight of a(co)polymer consisting of 1 or at least 2 ethylenically unsaturatedmonomers selected from styrene, α-methylstyrene, ring-substitutedstyrenes, acrylonitrile, methacrylonitrile, methyl methacrylate, maleicanhydride, N-substituted maleic imide and (meth)acrylates with 1 to 18carbon atoms in the alcohol component; C 0.5 to 60 parts by weight ofgraft polymer, obtainable by graft polymersation of at least twomonomers selected from the group consisting of chloroprene,1,3-butadiene, isoprene, styrene, acrylonitrile, ethylene, propylene,vinyl acetate and (meth)acrylates with 1 to 18 carbon atoms in thealcohol component; D 0.5 to 20 parts by weight of a phosphorous compoundof the formula (I)

in which R¹, R² R³ and R⁴, independency of each other, represent anoptionally halogenated C₁-C₈ alkyl group, or a C₅-C₆ cycloalkyl, C₆-C₂₀aryl or C₇-C₁₂ aralkyl group, each optionally substituted by at leastone of halogen and C₁-C₄ alkyl groups, n each, independently, represents0 or 1, N is 0 to 30, and X represents a mono or polynuclear aromaticgroup with 6 to 30 carbon atoms; E 0.05 to 5 parts by weight of afluorinated polyolefin; and F 0.01 to 50 parts by weight per 100 partsby weight of A to E of a very finely divided inorganic compound with anaverage particle diameter of less than or equal to 200 nm, saidinorganic compound being selected from Al₂O₃, AlO(OH), zinc borate andmixtures thereof, wherein the sum of the parts by weight of A to F is100 parts by weight.
 2. The molding composition of claim 1 wherein N informula (I) has a value from 0.3 to
 20. 3. The molding composition ofclaim 1 wherein said copolymer B is a random copolymer of styrene andacrylonitrile.
 4. The molding composition of claim 1, wherein, informula (I), R¹, R², R³ and R⁴ each, independently of each other,represent C¹-C₄ alkyl groups or phenyl, naphthyl or phenyl-C¹-C₄ alkylgroups, each optionally substituted with halogen and/or alkyl groups,and X is derived from diphenols selected from bisphenol-A, resorcinol orhydroquinone, which are optionally chlorinated or brominated.
 5. Themolding composition of claim 1, wherein the phosphorus compound informula (I) is at least one member selected from the group consisting oftributyl phosphate, tris-(2-chloroethyl) phosphate,tris-(2,3-dibromopropyl) phosphate, triphenyl phosphate, tricresylphosphate, diphenylcresyl phosphate, diphenyloctyl phosphate,diphenyl-2-ethylcresyl phosphate, tri-(isopropylphenyl) phosphate,halogen-substituted aryl phosphates, dimethyl methylphosphonate,diphenyl methylphosphonate, diethyl phenyl phosphonate,triphenylphosphine oxide, tricresylphosphine oxide andm-phenylene-bis(diphenyl) phosphate.
 6. The molding composition of claim1 wherein for formula (I), R¹, R², R³ and R⁴ are each phenyl, n is 1,and X is a divalent residue of bisphenol A.
 7. The molding compositionof claim 1 wherein N of formula (I) is from 0.5 to
 10. 8. The moldingcomposition of claim 1 wherein N of formula (I) is from 0.5 to
 6. 9. Themolding composition of claim 1, in which the average particle diameterof said inorganic compound F is less than or equal to 150 nm.
 10. Themolding composition of claim 1 wherein said molding composition furthercomprises 0.01 to 20 wt. %, with respect to the total moldingcomposition, of at least one further flame-resistant agent which isother than said phosphorous compound of formula (I).
 11. The moldingcomposition of claim 1, containing 10 to 90 parts by weight of componentA), optionally 2 to 30 parts by weight of component B), 1 to 40 parts byweight of component C) and 1 to 18 parts by weight of component D), 0.1to 1 part by weight of E) and 0.1 to 10 parts by weight of F).
 12. Themolding composition of claim 1 wherein said graft polymer C comprises agraft substrate C.2, said graft substrate C.2 being selected from adiene rubber, acrylate rubber, silicone rubber andethylene/propylene/diene rubber.
 13. The molding composition of claim 1containing at least one additive selected from the group consisting ofstabilisers, pigments, mold release agents, flow promoters andanti-static agents.
 14. The molding composition of claim 1, wherein thefluorinated polyolefin E is at least one member selected from the groupconsisting of polytetrafluoroethylene, polyvinylidene fluoride,tetrafluoroethylene/hexafluoropropylene copolymer, andethylene/tetrafluoroethylene copolymer.
 15. Molded items produced fromthe molding composition of claim 1.